Backyard Trip

[Missourian]

I continued my one-man Pennsylvanian summit....

 

After struggling to interpret poorly-exposed bits of Winterset Limestone, I was delighted to find this:

 

 

Again we have the Stark Shale and lower Winterset beds, along with the 'sandwich' beds I noted earlier.

 

Planolites traces are present in the Stark:

 

 

These sediment-filled tubes have been compressed into paper-thin impressions.

 

As at the other cut bank, the lower part of the Winterset is very well exposed here:

 

 

The first bed above the Stark is a soft, clayey bed of limestone (behind the lens cap) that is transitional between the shale and overlying limestone of the Winterset. The next bed up is similar in appearance, but is very dense and contains crinoid fragments. The lower 'bread slice' of the 'sandwich' form an overhang.

 

At a nearby spot, these same beds form an alcove that almost could be used as a shelter:

 

[Missourian]

As I walked upstream, I traced the 'sandwich' beds until some higher beds appeared:

 

 

I then worked my way up the slope. First, I noted a bit of Stark beneath the ledge so I was sure of which beds I was dealing with:

 

 

I took a closer look at the 'sandwich' here and found a few fossils that are rather conventional for Pennsylvanian limestones. They include crinoid stems:

 

 

And Juresania brachiopods:

 

[Missourian]

I then scrambled over to the more complete section of the lower Winterset:

 

 

There are three fairly distinct groups of beds here. The 'sandwich' beds are on the bottom. The massive, root-bearing bed is at the top. Between them are what I call the 'intermediate' beds. These are the local expression of three thick beds that can be seen in outcrops of the lower Winterset across the entire metro area. Here's a typical example twenty miles away in Independence, Missouri (courtesy of Google Street View):

 

 

Also, Kehbe may recognize these beds at his 'honey hole'.

 

I climbed up the steep slope to take a closer look at each level. Here, a distinct shale parting lies just above the 'sandwich':

 

 

Horizontal solution cavities in the root-mold bed betray bedding that is not apparent in most outcrops:

 

 

In the weathered zone at the top of the slope, larger cavities riddle the bed. A tree uses one for many of its roots:

 

 

It can't be seen in the image here, but there was a large animal burrow dug into one of these clay-filled holes. I didn't want to stick around long enough to meet the homeowner.

 

So this completes the lower part of the Winterset.

 

While walking in the creek bed, I encountered many chunks of chert:

 

 

 

These are typical of the upper Winterset. So it's very likely these potentially fossiliferous beds are exposed somewhere upstream. I ran out of time for today, but I will soon return to see what turns up.

[Missourian]

So are there any more exposures of Winterset further upstream? While driving through the area, I glimpsed some limestone in the creek. I figured—and hoped—this was the upper Winterset. A few days later, I made my way down there to check it out:

 

 

Upper Winterset indeed. Wow. There's so much going on here, I didn't know where to start. So I made my way down to the bottom of the section.

 

The root-mold bed is present:

 

 

I managed to find a couple tiny rootlets in its weathered face. I then followed the massive bed back over to the main outcrop:

 

 

The bed appears as the light gray, lumpy stuff beneath the ledge on the left. Its top is quite irregular. I'm not sure if this is due to the presence of a disconformity, or if that's how the rock weathers.

 

Speaking of the overhanging ledge, the thick, shelf-like bed looks like it may be bioclastic:

 

 

Up close, it is easy to see that it is made out of shelly debris:

 

 

When I made my way back up the creek, I noticed that this bioclastic bed was nowhere to be found:

 

 

It seems to have pinched out beneath the pile of boulders on the left. Does it pinch out on the other side? Lets take a look:

 

 

It's a little hard to make out, but it grades into shale as it thins out on the left. Due to its stratigraphic proximity to the root-bearing bed, it is likely that this is a cross section of a tidal channel that had been filled with shells. It is very similar to another upper-Winterset deposit I found about twenty miles to the east, as described at http://www.thefossil...ian-shell-beds/ .

[Missourian]

Yesterday, I returned to the Winterset exposure shown in the last post. I decided I wanted to collect and keep a certain fossil. I also took the time to follow up on a few details.

For one, I wanted to see what was underneath the bioclastic bed:

It turns out the top of the root-mold bed is irregular due to erosion soon after deposition:

The exposed limestone was scoured as it was exposed to the elements. Some time later, a paleosol was established. Eventually, the sea returned, and shelly debris filled in and smoothed out the rough spots.

The bioclastic bed itself is made up of abraded, sand-sized fossil fragments of an unknown nature, with Composita, fenestrate bryozoans and myalinids mixed in.

The paleosol is a crumbly, oxidized layer of clay:

In places, roots are present in the underlying limestone right up to the erosional surface:

The plants, most likely Cordaites, may have grown in the paleosol, or it is possible they grew in a spot a little higher up.

[Missourian]

Back upstream, the bioclastic bed is absent, but the strata are no less interesting:

 

 

In the base of the outcrop, there are a few feet of shale interbedded with lenses of limestone.

 

The paleosol is present as a rust-hued zone near the base:

 

 

Above that, there is platy, sandy shale that breaks off into shards:

 

 

Upon closer examination, it turns out this shale is filled with carbonized Cordaites leaves:

 

 

Some leaves up close:

 

 

Some of the interbedded limestone also contains leaves:

 

 

Unfortunately, this piece is badly weathered.

 

A loose chunk of limestone contains parallel strips of Cordaites wood:

 

 

I don't know whether these are stems or branches.

 

It is likely that these Cordaites produced the many roots that perforate the massive, weathered limestone bed below.

[Missourian]

In places, the shale has been partially calcified as large concretions:

 

 

It may be worthwhile to check these for Cordaites leaves.

 

This piece contains some Hypselentoma gastropods:

 

 

Higher up, concretions have coalesced into a nearly continuous bed:

 

 

The bedding of the original clastic sediments is preserved:

 

 

Between two concretions, fine-grained sandstone contains a sediment-filled burrow:

 

 

Notice how the uncemented beds were compressed after formation of the concretions.

[Kehbe]

I see these and other characteristics you post about on this thread, in different areas and outcroppings around town, and wonder to myself what kind of material or stone they are, how they came to be and what processes formed them. Then I read your posts and I have those 'ahaa' moments and slap myself on the forehead in a moment of understanding! Thanks Missourian! I absolutely enjoy your backyard trips and have learned much from them! Looking at these last few posts from you, I am convinced that this piece, http://www.thefossil...__fromsearch__1 is a filled and compressed burrow similar to what you have shown here. Keep on scouting and posting as you do us newbies a huge service with your reporting!

Thanks again!

p.s. Love the gastropod plate!

[Missourian]

On 4/21/2012 at 6:55 AM, Kehbe said:

I have those 'ahaa' moments and slap myself on the forehead in a moment of understanding!

 

I recently had such a moment with these Winterset beds, even though I've been poking at them for 20+ years. I'd notice the discontinuous beds and the weird lithology, but I hadn't given them much thought.

[Missourian]

There's a seemingly endless variety of beds here....

 

Back over above the bioclastic bed, there is some thin-bedded sandstone:

 

 

The contact point between the fossil debris and the sand is rather sharp:

 

 

Note the 'streamlined' concretion.

 

Not too far away, there is sandstone interbedded with shale:

 

 

The same area, with a camera flash:

 

 

When sunlight is lacking, I often take photos in both natural light and with a flash. Most of the time, the flash images are too flat to be of any use. But in this instance, I notice an odd sparkly area in the shale seam on the left. It looks like some shiny material. Is it coal? Perhaps, but I'd have to look at it again to be sure.

 

When I returned a few days later, I found this stuff in the spot:

 

 

Yes, that is a small lens of coal. It is likely an accumulation of Cordaites detritus.

[Missourian]

Above the concretionary beds, the strata are thick-bedded and quite cherty. The silica gives the rock a bluish color in the outcrop:

 

 

These beds appear to vary in thickness. I can't tell if they are cross-bedded or not.

 

The chert comes in many colors. Blue is characteristic of Winterset chert:

 

 

Here is some pink and white:

 

 

This irregular chert concretion has a palette of color:

 

 

Note the silicified gastropod just above my index finger. I think it is Strobeus.

 

There are quite a few pelecypods in some of these beds:

 

 

They are mostly Promytilus, along with a few Aviculopecten and a couple Derbyia brachiopods. The piece was laying in the rubble of a collapsed portion of the rock face.

 

This boulder is loaded with filled burrows:

 

 

They have been replaced with blue chert.

 

For the moment, these are all the outcrops I've been able to find in the creek.

 

Here is a stratigraphic chart for the creek exposures:

 

[Missourian]

Now we go back to the highest hill....

 

I recently returned to the highway interchange described here http://www.thefossil...post__p__305390 to collect some ironstone slabs from the Weston Shale to use for home decor.

 

While wandering across this Weston Shale slope,:

 

 

I stumbled upon an exposure of the South Bend Formation that was hard to spot from the road:

 

 

Most of the Little Kaw Limestone is exposed:

 

 

There are many small bryozoans visible on the top surface:

 

 

Better yet, the other two members of the formation are present here.

 

The Gretna Shale lies above the Little Kaw:

 

 

Higher up is the Kitaki Limestone. Although this unit is eight feet thick in Nebraska, it is merely an inch or so in thickness here. It is present as rubble strewn across the Gretna:

 

[Missourian]

What the Kitaki lacks in stature, it makes up for in fossils. The bed is made up in large part of fossil debris:

 

 

The fossils are chiefly crinoid fragments. The little brown lumps may be fecal pellets, according to one source.

 

These probably are burrow fills:

 

 

An algae-encrusted Delocrinus cup, possibly from the Gretna:

 

 

More chunks:

 

 

The one on the left with the Chonetinella brachiopods may be from the Gretna or Little Kaw.

 

The base of the Weston Shale can be seen as the barren, light gray shale near the grass:

 

 

The richness of the fossils in the Kitaki was a surprise. This is the kind of deposit that often turns up shark teeth. I'll have to return in the near future.

 

And here is a strat chart with a more complete South Bend:

 

[Missourian]

Not too far up the road from home is an exposure of Argentine Limestone. I hunted this ramp cut several years ago but didn't find anything. I decided to take a second look:

 

 

This cut contains most if not all of the Argentine.

 

As always, phylloid algae is present:

 

 

I had to take this one home with me. The little red specks are spider mites. Those little guys were everywhere.

 

As I walked along the outcrop, the bioclastic beds on top became 'looser':

 

 

Many fragments had broken away, which allowed me to find a couple goodies. The surfaces of the thin slabs contained a fine hash of standard Pennsylvanian fare:

 

 

Included in the mix are crinoid and echinoid fragments, brachiopods, and bryozoans. This piece features a nice fragment of fenestrate bryozoan:

 

 

Also present in the bioclastic limestone are several burrows:

 

 

Up close, you can see where the little critter scooped the mud and debris to the side of the hole:

 

[Missourian]

An interesting characteristic of the bioclastic beds here is the presence of cone-in-cone structures:

 

 

The round things may look like orbiculoid brachiopods, but they formed when calcite crystal growth deformed the original texture of the sediment, which was probably a thin parting of shale. This phenomenon also gives the surface a scaly or warty appearance.

From the side, these seams have a fibrous texture.

 

This recrystalized piece retains burrow traces:

 

 

In some cases, the calcite has broken away to reveal fossils beneath the crust. This piece features a horn coral and a trilobite pygidium:

 

[Missourian]

Here is an updated master stratigraphic column:

 

 

This chart represents approximately 300 feet of strata. Only a few small gaps remain.

 

The original image file was broken up into three equal parts to get around the 2500 pixel limit.

[LeeLeslie]

I'm new to this forum, but wanted to say that this thread has been a great education for another KC hunter.

Thanks so much!

[Bullsnake]

I'm new to this forum, but wanted to say that this thread has been a great education for another KC hunter.

Thanks so much!

You're so right! Now, if I could only be a better student.

Welcome to the forum!

[Missourian]

On 4/30/2012 at 3:46 PM, LeeLeslie said:

I'm new to this forum, but wanted to say that this thread has been a great education for another KC hunter.

Thanks so much!

 

Thanks much, and welcome to the forum.

[Missourian]

On Saturday, I stopped at an exposure of Spring Hill Limestone about a mile southeast of the spot described here http://www.thefossil...post__p__282417 . Instead of facing a 20-foot vertical cliff, I was able to walk along a gentle incline and sample the unit from all levels.

 

From where I parked, I started at the upper part of the limestone:

 

 

The top-most beds have a rusty color on fresh as well as weathered surfaces. It is possible that they were subjected to oxidation before deposition of the overlying Vilas Shale.

 

I hunted this portion at a nearby spot several years ago, and found a few poorly-preserved brachiopods, as well as this Peripristis tooth mold:

 

 

Below the rusty beds is a zone of wavy, almost concretionary limestone interbedded with thin shale partings. There weren't too many fossils to collect, but I did manage to knock off this interesting specimen:

 

 

It may be Heliospongia, but the structure appears a bit lighter than what I'd expect.

 

I didn't spot any other fossils here or in the massive bed below. Further down, little beds of calcareous shale contain quite a few fossils. The most common seem to be Neospirifer. Here, at least two can be seen near the contact with the limestone above:

 

 

 

These brachs are usually crushed or broken, but I did manage to find a fairly good one:

 

 

A few other brachiopods are present, as well as the bryozoan Fistulipora and large crinoid stems:

 

 

Below the shale beds is a zone of limestone containing nodules and lenses of black chert:

 

 

[Missourian]

As I walked along the cut, I reached the lowest beds of the Spring Hill:

 

 

The thick, tannish bed contains fossil debris:

 

 

It contains the usual mix of brachs, bryozoans, and crinoids, plus some fusulinids:

 

 

The beds of the Spring Hill make for some nice scenery:

 

 

A bit of the underlying Hickory Creek was beginning to become visible, but I soon ran out of outcrop.

[Kehbe]

Thanks for another great installment Missourian! I love the spirifer. and welcome to the forum LeeLeslie!

[LeeLeslie]

Thanks for the warm welcome. I look forward to see you all out in the field (provided we can pull our eyes off the rocks for a couple of seconds).

[Missourian]

When checking out an exposure of Winterset Limestone a couple weeks ago ( http://www.thefossil...post__p__322583 ), I found this limestone chunk with two strips of Cordaites wood:

 

 

I had left it in place, but when I saw some intricate detail in the photo, I returned to retrieve it. Once I cleaned it off and looked at it more closely, it turned out to be more interesting than I thought. The two strips of wood are actually branches or roots attached to a larger piece:

 

 

The flaring of the grain detail leads me to think this is a base with roots:

 

 

The bottom is broken off, so I'm not sure if it continued or not.

 

One root attachment shows a bit of structure:

 

 

The two root strips up close:

 

 

There is at least one root extending from the other side (left) of the base, but it is broken off:

 

 

In a few places, smaller roots and rootlets can be seen. These are similar to those present in the root-mold bed:

 

 

For reference, here's a reconstruction of Cordaites interpreted as a mangrove:

 

[Missourian]

Today, we visited the Shoal Creek Living History Museum. This is a "town" created with 19th-Century buildings that have been transplanted from various locations in the greater Kansas City metro area:

 

 

 

Large slabs of limestone used for walkways and retaining walls contain some history of their own. Large brachiopods and a few fenestrate bryozoans are easily spotted.

 

Here are a few Neospirifer and Antiquatonia brachs:

 

 

More of the same:

 

 

The largest brach of all is Echinaria:

 

 

These Linoproductus were larger in extent, but they are flattened:

 

 

Note the sponge borings on the shell on the left.

 

This bed may have come from the top of the Raytown Limestone. Some is exposed nearby in a small quarry: